1. Technical Field
This invention relates to a semi-transmission/reflection type liquid crystal display apparatus and more particularly to a color filter structure that makes a cell thickness of a liquid crystal display panel uniform.
2. Technical Background of the Invention
A semi-transmission/reflection type liquid crystal display panel that can perform both reflection type display utilizing external light and transmission type display by utilizing illumination light such as backlight is known (also known as a transflective display). This semi-transmission/reflection type liquid crystal display panel includes a reflection layer for reflecting external light inside a panel and allows illumination light from the backlight to transmit through the reflection layer. One of the reflection layers of this kind has a pattern having an opening (slit) of a predetermined proportion for each pixel of the liquid crystal display panel.
When this liquid crystal display panel is fitted to an electronic device such as a mobile telephone or a portable information terminal, it is fitted while a backlight is arranged at the rear portion thereof. In the liquid crystal display panel, external light transmits through the liquid crystal, is then reflected by the reflection layer, again transmits through the liquid crystal and emitted in the daytime or at a bright indoor place, thereby performing reflection type display. On the other hand, the backlight is turned on at night or in a dark place, the rays of light passing through the openings disposed in the reflecting layer from the rays of illumination light emitted from the backlight transmit through the liquid crystal display panel to thereby perform transmission type display.
In the liquid crystal display panel described above, a shading region called “periphery partition” or “frame edge” is formed to define an outer edge of an image display region. More particularly, a shading pattern having a substantially rectangular shape (hereinafter called “periphery partition”) is formed at positions corresponding to the outer edge of the image display region on two opposing substrates constituting the liquid crystal display panel. The periphery partition can be formed by laminating coloring layers of R (red), G (green) and B (blue) three colors in the same way as a black matrix formed inside a color filter.
When the periphery partition and the black matrix are formed through the lamination of the R, G and B coloring layers, however, a problem develops that a layer thickness becomes different between the periphery partition and the black matrix. The periphery partition is formed into a width of about 3 to about 4 mm on a plane of the liquid crystal display panel used for a mobile telephone, for example, whereas the black matrix inside the image display region is formed between adjacent pixels and has a width of only about 10 μm. Therefore, when the periphery partition and the black matrix are formed through lamination of the three R, G and B coloring layers as described above, each coloring layer can be formed to a design value at the periphery partition portion because the width is relatively great. However, it is extremely difficult to form the R, G and B coloring layers to the design values at the black matrix portion because the width is much smaller than at the periphery partition portion. Therefore, upper coloring layers of the laminated R, G and B coloring layers are likely to possess a smaller thickness. As a result, when the same step of forming each coloring layer to the same thickness is carried out, the coloring layers can be formed to a thickness substantially equal to the design values at the periphery partition portion but become smaller than the design values at the black matrix portion. Consequently, the layer thickness of the color filter layer becomes smaller as a whole at the black matrix portion relative to the periphery partition portion.
When the three R, G and B coloring layers are laminated to form the black matrix, the film thickness of the black matrix portion becomes structurally a maximum inside the image display region. However, since the periphery partition portion encompassing the image display region has greater film thickness than the black matrix portion as described above, a difference occurs in the cell gaps between the periphery partitioning portion and the image display portion inside the periphery partitioning portion. More particularly, the cell gap inside the image display portion becomes smaller. Therefore, non-uniformity of display resulting from nonuniformity of the cell gaps may occur particularly in regions inside the image display region close to the periphery partition.
In view of the problems described above, the present invention provides a substrate for a liquid crystal panel that can ensure uniformity of cells at a periphery partition portion and at an image display portion inside the periphery partition portion to prevent non-uniformity of display, its production method, a liquid crystal apparatus and an electronic apparatus.